In the prior art, there are many known methods and pipe fitting designs for connecting pipes to the various ports of industrial hydraulic pumps and manifolds to their associated reservoirs, for example. Such known arrangements often are provided by two or three-piece assemblies, including tapered pipe threads to attempt a leak-free seal. The prior pipe fittings are often associated with overcoming the problem of combining the industry standard S.A.E. "O"-Ring ports of various apparatus with standard American pipe and tubing.
Many of the prior fittings seek to provide methods of connection in hydraulic systems that use readily available adapters, pipes, and tubing. For example, as shown in FIG. 1, one known method incorporates an S.A.E. "O"-Ring by socket weld adapter 1 secured by a weld 3 over the end of a pipe or tubing 5. Typical practice is to test the assembly for leaks after welding, followed by pickling and cleaning of the assembly. The assembly is then installed via the threaded portion 7 of the adapter to a pump or manifold, and thereafter marked to align the bottom of the pipe or tubing 5 that is typically cut at a 45.degree. angle, thereby "customizing" the assembly to the apparatus in which it is installed. As a result, the prior assembly of FIG. 1, being custom fit to the apparatus in which it is installed, must be altered or marked for realignment if the apparatus is changed in the field. Note the use of an "O"-ring 6 on the annular groove 8 to provide a fluid sealing means.
As shown in FIG. 2, another common practice in the industry is to use a standard S.A.E. "O"-ring by taper pipe threaded adapter 9 combined with a taper threaded end 13 of pipe 11, with a sealing compound previously applied to the threads thereof, screwed into the female threaded end 15 of the adapter 9. The mated pipe 11 and adapter 9 are then coupled or installed on a pump or manifold via the male threaded end 17 of the adapter 9. The pipe 11 is tightened to a point where its bottom portion or bottom end (assuming a 45.degree. slant at the other end of pipe 11) is aligned in the direction of the particular fluid flow that is to be sucked into pipe 11, in this example. When apparatus is changed in the field, the assembly of the adapter 9 and pipe 11 must be altered to realign the assembly to the new apparatus. Note that a fluid sealing means is provided by mounting on annular groove 16 an "O"-ring 18.
In normal practice, the prior S.A.E. by socket weld adapter fitting 1 of FIG. 1, and S.A.E. by N.P.T. adapter fitting 9 of FIG. 2 are supplied by manufacturers thereof with thick or heavy walls in order to accommodate use for high pressure industrial hydraulic applications. As a result, such fittings 1, 9 may be modified by boring out their inside diameters to make the fittings 1, 9 have thinner walls, for use in low pressure hydraulics with maximum inside diameters to enhance fluid flow. The practice of remachining the fittings 1 and 9 adds to the expense of the use of such fittings for low pressure applications.
Parker U.S. Pat. No. 2,342,425, shows a pipe joint or coupling including a rubberized ring gasket 10 mounted on the threaded coupling end of a an elbow fitting 4 and compressively captivated between an inclined wall 11 of a projecting boss 2 of a mating port in a similar inclined wall 12 of a nut 8. A similar arrangement, is shown in Bashark U.S. Pat. No. 2,343,235, using different profiles for the inclined walls of the nut and port between which the rubberized sealing ring is held captive in compression for providing a leak-free seal.
Franck U.S. Pat. No. 3,101,206 shows the use of a nut 1 provided on an inner threaded portion of an end of a fitting, where the nut has downwardly projecting thin wall members 14 and 25 for providing an annular cavity for captively retaining a resilient sealing ring 14 on a flat sealing groove or inner end portion 20 of the fitting or elbow 12. After the outer threaded end portion 19, which is adjacent the sealing groove 20, is screwed into a port 11, as shown in FIG. 2, the nut is turned to move the captive sealing ring 14 and protruding deformable portion 25, 29 of the nut 13 into engagement with an inclined wall portion of the port means 11, for providing a fluid seal.
In Lasko U.S. Pat. No. 4,068,863, a pipe joint is shown for a non-industry standard application. It shows a mechanical pipe joint including a length of metal pipe having an annular external groove in one end portion, a compression ring disposed in the annular groove, and a compressible packing ring surrounding the end portion of the pipe. A companion pipe fitting part is provided having a bore in which the pipe end, the compressible packing ring and the compression ring are received. The tightening of a compression nut mounted on the companion pipe fitting causes shifting of the compression ring in the annular groove on the end of the metal pipe, in turn causing compression of the packing ring and a resultant seal between the outer surface of the metal pipe in the bore of the companion pipe fitting. Such an arrangement for a pipe fitting sealing mechanism is relatively expensive, and complicated by the increased parts count.
Bloom U.S. Pat. No. 2,759,743 teaches the use of a jam nut 18 provided with a rigid annulus 19 on its lower face for axially compressing a leather annulus 21 against an "O"-ring 17, for providing a fluid-type seal between the port of a boss 11 and the hydraulic fitting member 10.
In general, to reduce leakage between fittings, pipes, and ports of appparatus such as hydraulic pumps, some combination of an S.A.E. "O"-ring are typically utilized. Many high-pressure fittings and accessories are available for effecting such leakage-free coupling, but such fittings are not readily adaptable for low-pressure usage. Accordingly, low-pressure lines, such as pipes used for suction lines, are often connected to pumps using a customized and often haphazard arrangement of N.P.T. to S.A.E. adapters, pipes with tapered pipe threads, welded assemblies, and so forth as previously indicated.
On typical hydraulic power units with variable volume axial piston pumps, the low pressure inlet ports typically are horizontally oriented relative to the pool of fluid to be sucked into the pump. Accordingly, some type of elbow fitting or coupling fitting is required for connecting the vertically oriented suction pipe to the inlet port. Contrary to this, typical variable volume vane pumps typically include vertically oriented suction ports, only requiring a straight suction line to be connected between the inlet port of the pump and the pull of fluid to be sucked through the pipe into the pump. As previously indicated, the majority of available fittings and couplings for use with such low pressure pumping applications are either complicated assemblies requiring many piece parts, unreliable, unduly expensive, or only applicable as customized assemblies for use with a given pump apparatus. Many prior pipe fittings or couplings are prone to leakage, and may fail to provide sufficient flow area for fluid, resulting in undesirable pump cavitation.